The Red Devils midfielder suffered a hamstring injury during Tuesday’s 3-0 win over Basel.
Pogba lasted just 19 minutes at Old Trafford before he was forced to be withdrawn after over stretching for a tackle.
Jose Mourinho initially felt the France star would be out for a few weeks.
However, the time scale appears to be continually growing for when the 24-year-old is set to return.
According to The Times, initial MRI scans indicate a grade three tear with potential tendon damage.
Pogba is set to undergo further medical assessment.
But that is expected to confirm a lay-off period of ‘six weeks or maybe 12’.
The Times add United specialists believe Pogba may need 12 weeks of rehabilitation to fully recover.
And that would see him miss five Champions League games, plus Premier League clashes with a host of big rivals.
United face Liverpool, Tottenham, Chelsea, Arsenal and Manchester City in that spell.
Pogba’s absence will be a significant blow to Mourinho, with the ex-Juventus man having started the season brightly.
Manchester United, though, have alternatives in the form of Marouane Fellaini, Michael Carrick, Ander Herrera and Nemanja Matic.
